Acute and chronic pain management has been a concern for as long as medicine has been practiced. Several methods of inducing analgesia and anesthesia have been developed. For example, the use of chemical substances is perhaps the most common approach to pain relief which requires suitable substances that are effective, safe to humans, and do not cause complications or abnormal reactions. Despite the great advances that have been made in the field of anesthesiology, and in the field of pain relief in general, there are still some drawbacks to chemical-based approaches. For instance, the anesthetics generally available today must be administered in carefully graduated doses to assure the patient's well being, require extended periods of fasting prior to treatment, and are often accompanied by undesirable after effects such as nausea.
One alternative approach that is commonly used for providing pain relief is ablation in which nerves and/or tissue is removed and/or destroyed. Two approaches to removing tissue via ablation are through cold or hot ablation procedures and techniques. Various categories of ablation include but are not limited to electrical, radiation, light, radiofrequency, ultrasound, cryotherapy, thermal, microwave and hydromechanical. One form of hot ablation is radiofrequency ablation. During radiofrequency (RF) ablation, current passing through tissue from the active electrode leads to ion agitation, which is converted by means of friction into heat. The process of cellular heating includes almost immediate and irreparable cellular damage, which leads to coagulation necrosis. Because ion agitation, and thus tissue heating, is greatest in areas of highest current density (e.g., closest to the active electrode tip), necrosis is limited to a relatively small volume of tissue surrounding the RF electrode.
Another form of ablation uses cold ablation and is called cryoablation. During cryoablation, tissue is frozen or rapid freeze/thaw cycles are inflicted upon the tissue. There are many advantages to using cryoablation instead of radiofrequency ablation. For example, cryoablation is safer especially near critical vasculature and there is less risk of post-procedure neuritis or neuromas following neuroablation for the treatment of pain. Cryoablation allows treatment mapping pre and post procedure where areas of tissue can be mapped by limited, reversible and/or freezing. Cryoablation can be monitored and visualized on ultrasonography, CT and MRI. Moreover, because nerve cooling is anesthetic, cryoablation is a less painful procedure than thermal ablation techniques.
The current procedures and techniques using cryoablation used destroy tissue due to rupturing of cells and/or cell organelles within the tissue. Deep tissue freezing is affected by insertion of a tip of a cryosurgical device into the tissue, either transperineally, endoscopically or laproscopically, and a formation of, what is known in the art as, an ice ball around the tip. During freezing, ice formation within the extracellular space creates an osmotic gradient, resulting in cellular dehydration. Ice crystals then form within the cells causing cell membranes to rupture resulting in cell death.
In addition, when the adjacent tissues are present at opposite borders with respect to the freeze treated tissue and since the growth of the ice ball is in a substantially similar rate in all directions toward its periphery, if otherwise, the ice ball reaches one of the borders before it reaches the other border, and decision making must be made on whether to continue the process of freezing, risking damage to close healthy tissues, or to halt the process of freezing, risking a non-complete destruction of the treated tissue.
Traditional cryoablation systems can provide removal capabilities of soft tissue via the application of single needles that form an ice ball centered around a tip, but may also cause a high level of collateral thermal damage. Further, these devices may suffer from an inability to control the area of necrosis in the tissue being treated. The low temperature generated by these systems causes freezing of the surrounding tissue, leading to increased pain and slower recovery of the remaining tissue. Further, the desire for a cryoablation device to provide for effective ablation of soft tissue may compromise the ability to provide consistent ablation without significant collateral damage.
Another problem with currently available cryoablation devices is that they attempt to destroy tissue by using a single probe, which generates a large ice ball that creates a larger area for ablation. As a result, there is an increase in the amount of surrounding tissue damage near the surgical site.
Further, the health care practitioner may have difficulty positioning the tip of the device in the optimal location to get an optimal and consistent clinical result. This may also result in unwanted necrosis of adjacent tissue, which can lead to clinical adverse events including subsequent repair of the necrotic tissue.
Accordingly, there is a need for devices and methods to provide efficient destruction of nerve and/or soft tissue by ablating a larger surface area perpendicular to the device yet minimizing tissue damage proximal and distal to the device that can be used during a minimally invasive procedure and/or during an open surgical procedure. For example, along the length of the nerve. Further, there is a need for devices and methods that provide fine ablation capabilities of nerve and/or soft tissue. Devices and methods that do not cause a high level of collateral thermal damage and allow for the control of necrosis in the tissue being treated are also needed.